Why did humans develop a tolerance for lactose?

Did you know most of us are born lactose tolerant?

This is how almost all babies can drink breast milk without any stomach upset.

But then some time in early childhood genetics would take over and most of us would become lactose intolerant.

At least that is the way it used to be.

Somewhere along the way, a substantial portion of us started being able to ingest lactose-rich foods — milk, cheeses, etc. — without problems.

The question of how and why that happened is examined by writer Haley Weiss in The Atlantic.

People like to say that you are what you eat, but the truth is more like this: In the broad course of human history, we become what we eat. The contents of our ancestors’ dinner tables have slowly but surely left their signatures in the human genome. Learning to cook and soften our food was likely the major driver of our teeth shrinking during the Neolithic age. The lightening of Europeans’ skin is in part a product of dietary changes associated with farming.

The genes that let some adults drink milk with no attendant tummy troubles—a trait commonly called lactose tolerance—are a different story. A few different alleles, or versions of genes that influence a particular trait, can make for comfortable dairy consumption, and they’re all known for their unusually speedy spread.

A new study mapping European milk consumption throughout history suggests that humans owe the quick proliferation of lactose tolerance to a legacy of famine and disease that began thousands of years after we became dairy fiends. In other words, lactose-intolerant people have been throwing back dairy for thousands and thousands of years.

But whereas I think moaning to my boyfriend about my hot-girl tummy issues is just the sign of a tasty, tasty meal, our lactose-intolerant ancestors were more likely putting themselves through the digestive wringer just so they could survive.

You can read the rest of this fascinating article here.

Lactose, the molecule that launches countless bouts of diarrhea.

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